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The objective was to evaluate the effect of supplementation with selenized yeast, derived from a specific strain of Saccharomyces cerevisiae (CNCM I-3060), on productive and reproductive performance and on selenium concentrations in milk of grazing dairy cows. Multiparous Holstein cows (n=40), with an average body weight of 607±62 kg and a body condition score of 2.9±0.2 before parturition, were randomly assigned to 1 of 2 treatments. Control treatment consisted of a basal diet supplying 0.7 mg of Se.kg -1 dry matter. Experimental treatment consisted of the same basal diet supplemented with 3.0 mg of Se, from day 5 to 56 of lactation. Milk production, milk composition, SCC, and Se content of milk were determined at day 5, 14, 28, 42, and 56 of lactation. Blood samples from each cow were also taken during the same days, to measure glutathione peroxidase (GSH-Px) and Se concentration. To evaluate reproductive performance, the ovaries were examined by transrectal ultrasonography at days 22 and 57 postpartum. Days open, days to first service and services per conception were also recorded. Milk production, milk composition, and SCC did not differ between treatments during the trial. Selenium supplementation did not alter GSH-Px concentration (199.0 vs. 220.3 U.g -1 Hb) or Se concentration in blood (166.4 vs. 184.2 μg.l -1 ). However, organic selenium supplementation increased (p<0.01) Se apparent efficiency of transfer into milk (7.9 vs. 9.9%) and Se content of milk (12.7 vs. 20.5 μg.l -1 ); therefore, milk derived from cows supplemented with selenized yeast could be a useful way to contribute to daily intake of Se in humans, allowing to reach the daily dietary recommendations and helping as a functional food to solve problems related to Se deficiency.